Method of eliminating moisture from the surface of moistureabsorbent sheet material



Aug-22, 1950 P. ALEXANDER METHOD OF ELIMINATING MOISTURE FROM THESURFACE MOISTURE ABSORBENT SHEET MATERIAL Flled Apr1l 5, 1948 InventorAttorney 8 Patented Aug. 22, 1950 OFFICE I METHOD ELIMINATING MOISTUREFROM THE SURFACE OF MOISTURE- ABSORBENT SHEET .MA'TERIAL Paul Alexander,Berkhamsted, England Application April 1948, Serial No. 19,008 I This;invention relates to methods of eliminating moisture from the surface ofmoisture absorbent sheet material on which metal is to be deposited bythermal evaporation in a vacuum; and to apparatus for 'so treating thematerial.

In applicants United States Patent specification Number 2,402,269 thereis described a method of eliminating moisture from a moisture absorbentsheet material e. g. paper by heating one surface of the material in avacuum chamber by radiant heat, whereby the said surface is freed frommoisture without so far drying the whole body of the material as torender it undulybrittle. 1 r

The main object of the present invention is to devise an improved methodof treating moisture absorbent material .(such aspaper or transparentsheet material sold under the registered trade-mark Cellophane)containing plasticizers, such as g'lycerine which have a very low vapourpressure at atmospheric temperature.

According to the present invention a roll of the absorbent material isgradually unwound and progressivelyexposed in web form in a vacuumchamber (heating chamber) at a moderate vacuum (e. ggata pressure offrom 0.05 to 0.5 mm. of mercury) to radiant heat and passed out of theheating chamber whilst hot to a communicating re-rollingchamber adaptedto be vacuumized, the pressure in the vacuumized re -rolling chamberbeing maintained at a higher pressure than that inthe vacuumized heatingchamber, whereby one surface only of the web is freed of the plasticizerand the vapour of the plasticizer is prevented from gaining access, tothe re-rolling chamber.

By the present invention the is re-rolled without exposing the treatedsurface when cooled to the vapour evolved from it during the heattreatment, andmay be thereafter coated in a separate vacuum chamber witha metal by the 'known thermal evaporation methods; This depositioncannot be. commercially performed in the re-rolling chamber because thelow pressure required could not be economically maintained in theheatinchamber.

ThB present invention also comprises apparatus for depriving one surfaceof a moisture ab sorbent material in, web form of a plasticizer, such asglycerinawhich has a very low vapour pressur'eat atmospheric temperaturecharacter ised by two chambers adapted to be vacuumized, one of saidchambers (the heating chamber) con-. taining a heater providing radiantheat for'the web, and the other (the re.-rolling chamber) heatedmaterial I 4 Claims. (01. 34 -16) containing a take'up roll, the heatingchamber communicating with the re-rolling chamber only by one ortwoslits in the wall of the heating chamber through which the webpasses, the slit through which the web passes out of the heating chamberbeing situated so close to the heater that the web leaves the heatingchamber whilst still hot, the two chambers being evacuated by exhaustingmeans connected to the heating cham-. ber so that the re-rolling chamberis evacuated solely by flow of gas from it into the heating chamberthrough the said slit or slits.

The supply roll may be in the heating chamber in which case only oneslit will be required in the wall of the heating chamber or may bedisposed together with the take up roll in the-rerolling chamber inwhich latter case two slits are required in the wall of the. heatingchamber... By such arrangement the two chambers are simultaneouslyevacuated whilst maintaining a lower pressure in the heating chamberthan in the re-rolling, whereby there is a continual flow of gas fromthere-rolling to the heating chamber and vapour evolvedin the lattercannot pass .25 to the re-rolling chamber.

The re-rolled material is removed from the re-rolling chamber and thenmounted in an independent vacuumchamber on which metal deposition iseffected under a very much lower pres sure.

. In order that the invention may be more clearly understood referencewill now be made to .the accompanying diagrammatic drawings, whichshowby way of example preferred embodiments of the presentinvention Inthe drawings: b a Figures 1 and, 2 are sectional views showing theheating andre-rolling chambers, the supply roll being outside theheating chamber in Figure l and inside the heating chamber in, Figure 2.

' Figure 3 is .a sectional view showing a modificationof the arrangementshown in Figure l. The same reference numerals indicate similar parts inthe two figures. v r,, The vacuum chamber l, herein termed the heatingchamber, is enclosed within a chamber 2, herein termed there-rollingchamber, the chamber l containsthe source of radiant heat constituted byan electric heater 3. 1

Referring first to Figure 1, a web of material 41in the manufacture ofwhich glycerine has been used as a plasticizer), emanating from a supplyroll 5 in the re-rolling chambennpasses over a guide roll Band through aslit 1 in the wall of theheating chamber. In the heating chamber theface of the web intended eventually to be coated, by condensationthereon of the Vapour of metal produced by thermal evaporation in avacuum, passes in front of the heater 3, thence over a guide roll 8, andout of the heating chamber 1 through a second slit la in the wall of thechamber, hence over a guide roll 9 to the take-up roll H1, in there-rolling chamber 2, driv en by a clockwork motor indicated at H.

The arrangement is similar in Figure 2, except that the supply roll isin the heating chamber I, and there is, therefore, only one slit, la, inthe wall thereof through which slit the strip 4 passes out of theheating chamber into the re-rolling chamber.

The vacuum in the heating chamber I is maintained at a lower pressurethan the vacuum in the re-rolling chamber, so that any flow oi air orvapour between the two chambers is in the direct n w i h is from thererollin chamber .2 to h h ting h mb r 1; his ff c s brou h about byevacuating the two chambers through a ng p ssa e l2 located in t e wa lof the heating chamber I and connected directly to the p mpin ppa t s, Asuitable vacuum in the heating chamber is a pressure of about 0.1 min.of mercury.

It may be noted that the web of material passes out of the chamber Iwhile it is still too hot to 3 for carrying out the invention, the twochamhers a e m d by a pa tition wall a within a single vacuum chestwhich partition divides the chest into the two chambers I, 2. The vacuumpump I2 is connected tg the heating chamber, and the re-rolling chamber2 is evacuated by flow of gas through two slits, I, "la in the partitionIa into the heating chamber I,

Similarly, the construction shown in Figure 2 m y b m fied y d vi ingthe outer chamber by a partition and arranging the supply roll in theheating chamber, as will be readily understood.

By using s h f rms o apparatus lycerine is effectively vapourised fromone Surface of absorbent material, for example paper or that transparentmaterial sold on the open market under the registered trade-markCellophane, and the vapour is removed from the material whilst hot, sothat there is no possibility of glycerine vapours condensing on thecooled material as it is being re-rolled.

I claim:

1. A method of eliminating moisture from the surface of a moistureabsorbent. sheet material, on which surface metal is to be deposited bythermal evaporation in a vacuum, comprising p ss v ly u ro l n and expoing a web of moisture absorbent sheet material to radiant heat in avacuumised heating chamber, passing the said material into a vacuumisedire-rolling chamber communicating with said heating chamber only by arestricted opening or openings sufficient to permit of passa e of thematerial from one said chamber to the other, and rolling the saidmaterial into roll ,form in said re-rolling chamber whilst it is stillhot from heat exposure in said heating chamber, the vacuum. in saidheating chamber being maintained by connecting said heating chamber toan evacuating pump, and the said re-rolling chamber being vacuumisedsolely by flow of gas thereirorn 4 into said heating chamber throughsaid opening or openings, said flow of gas thereby precluding egress ofmoisture from said heating chamber through said opening or openings intosaid rerolling chamber.

2. An apparatus of the kind described, comprising a vacuumised heatingchamber, a vacuumised ree-rolling chamber immediately adjoining saidheatingchamber, a supply roll for supplying moisture absorbent materialto be treated, a radiant heat source in said heating chamber, restrictedaperture means for establishing communication between said heatingchamber and said re-rolling chamber, means for progressively conductinga web of moisture absorbent material gradually unwound from said supplyroll past said heat source with one surface thereof exposed to said heatsource and through said aperture means int said re-rolling chamber,vsaid aperture means bein dispo d in uch proximi y to said heat sourcethat said m t rial enters said re-rolling chamber wh ls still hot, atake-up roll in said re -rolling chamher for converting aid hot materialinto roll form, and exhausting means connected to s heating chamber formaintaining a desired vacuum h r in, said re-rolling chamber beinvacuumised solely by flow of gas therefrom through said aperture meansinto said heating chamber, said flow of gas thereby precluding egress ofmoisture from said heating chamber throu h said ap r ure means into saidrer 11ine chamber.

3. An appar us of the kind described. mprising. a vacuumised heatingchamber, a va mise r -rolling chamber, one of said chambers b in dispoed wi hin the. other s id chamber, a supply roll in said re rollingchamt for supplying m i ture absorbent materi l to be treated, a radiantheat source in said heatin cham er, first r tricted apertur m a pmitting of the passage of said material from said re-rolling chamberinto said heating chamber, second restricted aperture. means for passingsaid material out of said heatin chamber into said re-rolling chamber,means for progressively conducting a w b of moisture absorbent m t ri lgradually unwound from said Supply roll through said first aperturemeans past saidv heat source with one surface thereof exposed to saidheat source and through said second aperture means into said re-rollingchamber, said secondv aperture means being disposed in such proximity tosaid heat source that said material enters said re-rolling chamberwhilst still hot, a take-up roll in said re-rolling chamber forconverting said not material into roll form, and exhausting meansconnected to said heating chamber for maintaining a desired vacuumtherein, said rerolling chamber being vacuumised solely by flow of gastherefrom through said aperture means into said heating chamber, saidflow of gas thereby precluding egress of moisture from said heatingchamber through said, aperture means into said re-rolling chamber,

4. An apparatus of the kind described, comprising a vacuumised heatingchamber, a vacuumised re-rolling chamber, one of said chambers beingdisposed Within the other said chamber, a pply roll n said heatingchamber for supplying oisture absorbent material to be treated, aradiant heat source in said heating chamber, restricted aperture meansfor estabchamber and said re-roll'ing chamber, means for such proximityto said heat source that said material enters said re-rolling chamberWhilst still hot, a take-up roll in said re-rolling chamber forconverting said hot material into roll form, and exhausting meansconnected to said heating chamber for maintaining a desired vacuumtherein, said re-rolling chamber being vacuumised solely by flow of gastherefrom through said aperture means into said heating 5 2,402,269

chamber, said flow of gas thereby precluding egress of moisture fromsaid heating chamber through said aperture means into said re-rollingchamber.

- PAUL ALEXANDER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 839,191 Passburg Dec. 25, 1906921,307 Strohn May 11, 1909 2,384,500 Stoll Sept. 11, 1945 Alexander eta1. June 18, 1946

